When an invalid texture is passed to setObjectTexture or setObjectTextureGlobal a warning message shows up on screen and no effect can be observed.
When passing an empty string "" instead, the specific hiddenSelection texture becomes invisible.
Short video (hosted on Twitter) can be found under this link: https://twitter.com/i/status/1452329190284533764
Place down a vehicle (must have hiddenSelections defined in its config) in the editor and set the texture of one (if not all) hiddenSelections to an empty string via
_object setObjectTexture [#, ""];
Where # is the number of the hiddenSelection defined in the model's config, starting with 0.
The same effect can be observed when the global version of the command (setObjectTextureGlobal) is used.
Repro mission (SP) can be found under this link: https://www.dropbox.com/sh/35204jhnvfofza0/AABF0Vew2xfUkXZpYHvj8UpMa?dl=0
This has the potential to be exploited by cheaters in MP.
This is intentional and used by many mission makers.
If cheaters can freely execute scripts in MP you have a much bigger issue than just partially invisible vehicles.
if they want invisible vehicle they can just do hideObject and have a much simpler and better way to become invisible.